Noise from switching regulators can cause a part (e.g., processor) or platform to exceed EMI (electro-magnetic interference) specifications which may prevent the part or platform from being shipped or sold. Noise from switching regulators can also cause interference with a platform radio causing performance loss if the switching noise harmonics are present in the radio band. A typical solution to the above problem is to use Faraday cage shield for the switching voltage regulator. However, when switching voltage regulators are integrated on-die with other interfering circuits, Faraday cage may not be a viable solution.
Finite inductance and limited output decoupling capacitance in a buck DC-DC converter (e.g., Voltage Regulator) causes the output voltage of the converter to droop when output current suddenly increases. This can be a problem especially for the core supply (generated by the voltage regulator), with the highest di/dt. Voltage regulator (VR) may provide the supply for most voltage domains on a CPU (Central Processing Unit). The switching of high currents in a DC-DC converter at high di/dt may lead to electromagnetic emissions at the fundamental and at harmonics of the switching frequency, which cause electromagnetic interference (EMI) and radio frequency interference (RFI—seen by a receiving radio in the platform). Unmitigated EMI and RFI from the CPU can lead to increased platform cost and/or reduced battery life and can even cause the CPU to fail EMI testing.